Fuel control for exhaust turbine power plants having internalcombustion gas generators



FUEL. CONTROL FOR EXHAUST TURBINE POWER PLANTS HAVINGINTERNAL-COMBUSTION GAS GENERATORS 6 Sheets-Sheet 1 Jan. 22, 1952 R JcoAR Filed Feb. 6, 19 45 THEY/5'7 NOZZLE TURBINE FIG.

INVENTOR RICHARD J. COAR ATTORNEY Jan. 22, 1952 R J CQAR 2,583,470

FUEL. CONTROL FOR EXHAUST TURBINE POWER PLANTS HAVINGINTERNAL-COMBUSTION GAS GENERATORS Filed Feb. 6, 1945 6 Sheets-Sheet 2INVENTOR RICHARD J. COAR FIG. 52 ATTORNEY Jan. 22, 1952 com 2,583,470

FUEL CONTROL FOR EXHAUST TURBINE POWER PLANTS HAVING INTERNAL-COMBUSTIONGAS GENERATORS Filed Feb. 6, 1945 6 Sheets-Sheet 5 XX if FIG. 3

INVENTOR RICHARD J. COAR ATTORNEY Jan. 22, 1952 J CQAR 2,583,470

FUEL CONTROL FOR EXHAUST TURBINE POWER PLANTS HAVING INTERNALCQMBUSTIONGAS GENERATORS Filed Feb. 6, 1945 6 Sheets-Sheet 4 as H0 H2 98 FIG. 4

INVENTOR RICHARD -J. COAR CMW ATTORNEY Jan. 22, 1952 R. J. COAR FUEL.CONTROL FOR EXHAUST TURBINE POWER PLANTS HAVING INTERNAL-COMBUSTION GASGENERATORS 6 Sheets-Sheet 5 Filed Feb. 6, 1945 Dn Rm 06 T w .N% E

m Wm ATTORNEY Jan. 22, 1952 R. J. COAR FUEL. CONTROL FOR EXHAUST TURBINEPOWER PLANTS HAVING INTERNAL-COMBUSTION GAS GENERATORS 6 Sheets-Sheet 6Filed Feb. 6, 1945 E: mum woznonw 2 OF CONTROL LEVER MOTION FIG. 6.

INVENTOR RICHA D J. COAR ATTORNEY Patented Jnn. 22, 1952 FUEL CONTROLFOR EXHAUST TURBINE POWER PLANTS HAVING INTERNAL- COMBUSTION GASGENERATORS Richard J. Coar, Hartford, Conn., assignor to United AircraftCorporation, East Hartford. Coma, a corporation of Delaware ApplicationFebruary a, 1945, Serial No. 516,490

6 Claims. (Cl. Gil-39.28)

The invention relates to fuel controls for power plants of the type inwhich one or more internal combustion engines provide a supply of gasunder pressure which may be additionally heated in a burner for drivinga turbine.

In this type of power plant the supply of fuel to the engine or enginesand the burner is de-- pendent upon power requirements of the turbine.For example, under normal operating conditions the burner may be off.and all of the fuel used is delivered to and burned in the engines inwhich case the burner becomes operative only at loads above normal. Afeature of this invention is a control for the fuel supply so that thesupply of fuel to the power plant may be accurately measured andcontrolled and also properly divided between the engines and the burnerdependent upon the power requirements.

Power plants of this type may be used in aircraft and are, therefore,subject to operation under varying pressure conditions. A feature of theinvention is the automatic compensation for changes in the atmosphericpressure which would provide for decreasing the fuel in accordance withdecreasing pressures.

The supply of fuel may be controlled by variable orifices withassociated controlling mechanisms. In order that-such orifices mayaccurately measure the fuel delivered the pressure drop across theorifices must be controlled. A feature of the invention is anarrangement for maintaining the desired pressure drop across theorifices, thereby assuring accurate measurement of the fuel.

The source of power may be, as above stated, a number of internalcombustion engines, each of which may be a combined engine andcompressor unit in which the compressor supercharges the engine so thatthe exhaust gas is delivered at a higher pressure. In the event offailure of one of the units the fuel delivered to the engines issupplied to the remaining units. thereby subjecting these other units tooverload conditions, especially when the power plant is operating nearfull load. A feature of this invention is a pressure relief arrangementby which the degree of overload on the units may be controlled in theevent of failure of one or more of the units to operate. 1

When the power plant is operating at or near full load the failure ofone or more ofthe engine units would result in a sudden and continnedloss of power. Another feature of the invention is a load compensatingvalve which will deliver to the oil burner the fuel not used by the 2remaining engine units. thereby maintaining substantially the samepower.

Other objects and advantages will be apparent from the specification andclaims, and from the accompanying drawings which illustrate anembodiment of the invention.

Fig. 1 is a diagrammatic view of a power plant for which the fuelcontrol is adapted.

Fig. 2 is a sectional view through one of the engine units.

Fig. 3 is a sectional view showing diagrammatically the fuel control.

Fig. 4 is a fragmentary view of a part of the fuel control of Fig. 3showing the fuel control orifices and their associated mechanism.

Fig. 5 is a view of a part of the fuel control of Fig. 3 showing themechanism by which the pressure drop across the orifices may becontrolled.

Fig. 6 is a diagram of the fuel flow requirements.

The generators or engine units Ill supply hot gas under pressure througha duct l2 to the inlet of the turbine H. The latter is conected bypropeller system l5 through gear reduction units (8 and 20 and shafts 22and 24. The turbine exhaust discharges as a jet through a restrictednozzle 26 which may be directed rearwardly of the aircraft to produce anadditional propulsive thrust.

The gas is heated between the generator and the turbine by dischargingfuel into duct 12 through a fuel nozzle 30 supplied by a fuel line 32.

Fuel is admitted at a point spaced far enough from the turbine to assurecomplete burning of the fuel before the power gas has reached theturbine inlet.

As shown in Fig. 2 each engine unit is in the form of a free-pistonengine and compressor unit comprising an engine cylinder 34 havingreciprocating pistons 36 and 38 to which compressor pistons 40 and 42 incylinders M and 46 are integrally connected. Sleeves II and 8! attachedto the compressor pistons complete the reciproeating piston assemblies.The sleeves in combination with pistons 52 and 54 over which theyreciprocate form air spring cylinders.

The piston assemblies are moved apart by the burning of fuel iniectedinto the engine cylinder between the engine pistons. Air compressed inthe air spring cylinders on the power stroke returns the pistonassemblies. The assemblies are maintained at equal distances from thecenter of the engine cylinder by a linkage of which rods 55 may form apart.

Intake manifold 56 conducts air to sets of intake valves 58 throughwhich air alternately enters opposite ends of the compressor cylinders.The compressed air reaches the cylinders through sets of dischargevalves 60 also at opposite ends of the compressor cylinders and passesthrough scavenge manifold 62 and through ports 64 which are uncovered bypistons 36 and 38 at the end of the power stroke. Air entering theseports is blown through the engine cylinder and discharges throughexhaust ports 66 into exhaust manifolds 68, Figure/ 2;

The intake manifolds of the several units are connected to an intakeduct 10. The scavenge manifolds are interconnected by a pipe 12. Theexhaust gases flow from the exhaust manifolds through pipes 14 into ductI2.

As shown in Figure 1, fuel under pressure is delivered through a conduit16 to a fuel control device shown in section in Figs. 3 and 4. Thisdevice has a control valve which includes a sleeve 80, Fig. 4, turnablein a cylinder 82 and having a projecting stem 84 by which the sleeve maybe turned. A pin 86 engages a circumferential slot 81 in the sleeve tohold. the sleeve against axial movement in the cylinder. Sleeve 80 has aport 88 in line with a passage 89 from the conduit 16 through which fuelenters the cylinder 82 and an outlet port 90 through which fuel for thegenerators and the burner is metered. Fuel flows through channels 92 and92A and a duct 93 to the injection pumps 94, Figure 1, for theindividual generators. Fuel for the burner flows from channel 92 througha channel 96 to a port 98 in sleeve 80. This burner fuel is then meteredthrough an outlet port I in sleeve 80 to the passages I02 and I02A whichconnect with duct 32, Fig. l, to the nozzle 30.

A spool valve I04 located within sleeve 80 has a port I06 cooperatingwith port 90 in sleeve 80 for metering the flow of fuel and another portI08 cooperating with port I00 in metering the burner fuel. This spoolvalve also has a cen tral plug IIO which prevents flow of fuel betweenport 88 and port 98 in sleeve 80. Pin 86 engages an axial slot H2 inplug IIO to prevent turning of the spool valve although permitting axialmovement of the valve.

Ports 90 and I06 cooperate to form a metering orifice for fuel intochannel 92 and ports I00 and I08 form a metering orifice for fuel intochan-. nel I02. Since sleeve 80 turns without linear movement, and spoolvalve I04 reciprocates without turning movements the overlapping portsmove at right angles to each other. In this way, the fuel flow throughthe orifice may be made I26 has outlet ports I32 and I34 connected byconduits I36 and I38 to opposite ends of the cylinder 82 in which thespool valve is slidable. Valve plunger I24 alternately connects inletport I28 to the outlet ports, and by admitting fuel under pressure toone end or the other of the cylinder 82 causes axialmovement of thespool valve I04. It will be noted that one end of sleeve valve 80 isopen so that the fuel pressure acts directly on the spool valve I04, andat the other end the sleeve valve has p01 s I46 so that the fuel underpressure may act directly on this endof the spool valve. By connectingthe plunger I24 to link II6 the servo causes spool valve I04 to move anamount proportional to the movement of the central member I22 of thepressure sensitive bellows.

In order to obtain the desired motion for the central member I22 thebellows system includes an evacuated bellows I42 acting on one side ofthe central member and another bellows I44, the inside of which is opento the atmosphere Y through a passage I46.

factorially proportional to the motion of each v changes the centralmember I22 of the bellows to which link H8 is connected moves laterallyand operates through a servo-motor to cause the spool valve to moveaxially.

As shown in Figure 4 the lever II6 has connected to it a valve plungerI24 slidable in a bore I26 having an inlet port I28 connected by apassage I30 connected to fuel inlet passage 89. Bore The particularshapes of the outlet ports 90 and I06 which cooperate to meter the totalfuel flow through the control valve are selected to obtain the desiredflow characteristics. It will be apparent that the flow rate is changedeither by turning of sleeve valve or by axial movement of spool valveI04. The same is true of ports I00 and I08 which cooperate to meter theflow of fuel to the burner. In order better to understand the desiredoperation of the fuel controls the desired results are shown in thegraph of Figure 6. As shown, the total fuel flow at sea level is greaterthan the total fuel at altitude and it is obvious that the fuel flowwill vary between the two total fuel flow lines on the chart dependingupon the altitude at which the power plant is operating. The burnerbegins to operate only at a predetermined setting of the main controllever at which point ports I00 and I08 move into alignment to permitflow of fuel to the burner. The arrangement is such that the burner fuelis taken away from the total fuel as metered by ports and I06 so thatthe remaining fuel is delivered to the generators. Thus for all loads onthe power plant, the ports 90 and I06 cooperate to meter the total fuelflow to both burner and generators, and the ports I00 and I08 cooperateto meter the fuel to the burner.

A constant pressure drop across the metering ports is maintained so thatthe fuel will be proportional to the area of the port opening. This isaccomplished by plunger valves I48 and I50 controlling the flow area ofpassages 92 and I02 respectively. As shown in Fig. 5, the plunger valveI48 between channels 92 and 92a is controlled by a relay valve I52,slidable in a bore I 54 and normally moved downward by a spring I56. Thelower end of bore I54 is connected by a channel I58 to inlet passage 89.The other end of bore I54 is connected by a channel I60 to passage 96.Bore I 54 has an inlet I62 connected by a channel I64 to the channelI58, and the plunger I62 alternately admits fluid from port I62 tooutlet ports I66 and I68. These outlet ports are connected respectivelyto the right and left hand ends of the bore I10 in which the plungervalve I48 is slidable. Throttle vents I12 and I14 permit discharge offluid from bore I10, these vents being connected by a channel I16 to anoverflow or drain channel I18. By the use of device, as the pressure-inchannel 92 drops with respect to the pressure in inlet channel 80. relayvalve I52 moves upward causing fluid to enter the right hand end of boreI to move the plunger valve I48 to the left, thereby closing the passagearea in channel 92. The fuel flow from channel 92 to 92a around a.reduced central portion I80 of the plunger valve is thus restricted. andthe pressure in channel 92 increases, until the pressure differencebetween channel 89 and channel 92 becomes equal to the valuepre-selected by spring I56.

The control for the pressure drop across the ports I00 and I08 thatcontrol the burner fuel is operated in asimilar manner. A relay valveI82 is connected at opposite ends to the channel 98 and the channel I02respectively as by channels I84 and I86. Bore I88 for valve I82 has aninlet port I90 and spaced outlet ports I92 and I94, connected toopposite ends of the bore I96 in which plunger valve I is slideable.Discharge vents I98 and 200 for the opposite ends ofbore I98 areconnected to the channel I18.

It may be advantageous to have a pressurerelief valve to preventoverloading of the fuel pumps supplying fuel to channel 89. Toaccomplish this, the inlet passage 89 is interconnected by a crosspassage 202 to the drain passage I18. A spring loaded valve 204 normallycloses passage 202. In addition to the spring 206 holding the valve 204closed, pressure from channel 92A is applied to bellows 208 by conduit2I0. If the pressure difference across the metering ports 90 and I08plus that across the plunger valve I48 becomes excessive, that is, ifthe pressure difference between inlet passage 89 and outlet passage 92Abecomes excessive, the valve 204 will open. reducing the pressure inpassage 89 by bleeding off fluid to drain I'IB.

Valve 204 also maintains a calibrated sensitivity in plunger valve I48and prevents possible vapor formation accompanying high pressure dropsacross valve I48.

It may be advantageous to have a pressure relief valve in the generatorfuel supply channel, so that in case of failure of one or more of thegenerators to operate, the remaining generators are not overloaded. Toaccomplish this, a plunger 2I2 fits in a sleeve 2I4, which is slidablein a bore 2I6 and which may be adjusted axially by a gear 2 I8. A spring220 within an evacuated bellows 222 in a chamber 224 and acting onplunger 2 I2 balances the pressure in channel 92A which acts on the endof the plunger. The sleeve connects channel 92A and channel 224 and hasports 225 normally closed by the plunger 2I2. When the pressure inchannel 92A becomes excessive. under conditions of generator overload.the plunger 2I2 is displaced to the right and uncovers ports 225 topermit fuel to flow from channel 92A into chamber 224.

It is seen that the position of the plunger 2I2 is determined by theabsolute pressure in channel 92A, by virtue of the evacuated bellows222. Further, the sleeve 2 I4 is slidable within the bore 2I6. and isactuated by the gear 2I8, so that the absolute pressure within channel92a at which parts 225 open, can be controlled by rotation of the gear2I8. Gear 218 .may be linked to the main control shaft 84, asdiagrammatically represented in Fig. 3, so that the degree of overloadcan be made a function of main control lever position.

The fuel from chamber 224 passes into a bore 228. where it is deliveredby a selector valve 230 either through conduit 226 to the burner supplychannel I02A, or through a conduit 232 to drain I18. Valve 230 isslidable within the bore 228. This bore is open at the bottom to thepressure of channel 98 by a conduit 235, and at the upper end to thepressure of channel I02 by way of conduits I88 and 286. The selectorvalve 230 is loaded at the top by spring 234.

At low generator outputs, whenever port I 00 is closed, as determined bythe rotation of the main control shaft 84, the fuel vented from channel92A by valve 2I2, under generator overload conditions. passes fromchamber 224 into drain I18. This results from the high pressuredifference between channels 98 and I02, which occurs when there is noflow through port I00. This high pressure difference moves the selectorvalve 230 upward, against the spring, so that conduit 232 is open. andconduit 226 is closed by the valve.

If one or more of the generators should fail at high power, however, itmay be advantageous to deliver the fuel not used by the generators tothe oil burner circuit, essentially recovering the loss in power. Athigh power operation, the port I00 is open, and the pressure differencebetween channel 96 and channel I02 is controlled to a predeterminedvalue by the relay valve I82. This pressure difference is not enough toovercome the force of the spring 234, and the selector valve 280 isforced to the bottom of bore 228, thus opening conduit 228 and closingconduit 232.

It is to be understood that the invention'is not limited to the specificembodiment herein illustrated and described, but may be used in otherways without departure from its spirit as defined by the followingclaims.

I claim:

1. Fuel flow controlling means for a power plant including a number ofinternal combustion gas generators, and a burner through. which gas fromthe generators passes and in which additional fuel is burned. said fuelflow controlling means including a supply conduit and branch conduitsfrom the supply to the generators and to the burner, a metering orificein the branch conduit to the generators for controlling the fuel flow tosaid generators, another metering oriflce in the branch conduit to theburner for controlling the fuel supply to said burner, one of saidorifices including sleeves having overlapping openings through which thefuel flows, and means separately adjusting said sleeves, and one of saidsleeves having an opening forming a part of the other metering orificewhereby both orifices may be adjusted simultaneously.

2. Fuel flow controlling means for a power plant including a number ofinternal combustion gas generators, and a burner through. which gas fromthe generators passes and in which additional fuel is burned, said fuelflow controlling means including a supply conduit and branch conduitsfronrthe supply to the generators and to the burner, a metering orificein the branch conduit tothe generators for controlling the fuel flow tosaid generators, another metering orifice in the branch conduit to theburner for controlling the fuel suppl to said burner, each of saidorifices including relative movable elements having overlapping openingsthrough which the fuel flows, means for adjusting the elements for eachof said orifices separately, and one element of one orifice beingconnected to and moving with one of the elements of the other orifice.

3. Fuel flow controlling means for a power plant including a number ofinternal combustion gas generators, and a burner through which gas fromthe generators passes and in which additional fuel is burned, said fuelflow controllin means including a conduit supplying fuel to thegenerators, and another conduit supplying fuel to the burner, aconnection between the conduits, and a valve responsive to pressurechanges in said first conduit for controlling the flow through saidconnection.

4. Fuel flow controlling means for a power plant including a number ofinternal combustion gas generators, and a burner through which gas fromthe generators passes and in which additional fuel is burned, said fuelflow controlling means including a conduit supplying fuel to thegenerators, and another conduit supplying fuel to the burner, aconnection between the conduits, and a valve responsive to pressurechanges in said first and second conduits for controlling the flowthrough said connection.

5. Fuel flow. controlling means for a power plant including a number ofinternal combustion gas generators, and a burner through which gas fromthe generators passes and in which additional fuel is burned, said fuelflow controlling means including a conduit supplying fuel to thegenerators, and another conduit supplying fuel to the burner, aconnection between the conduits, and a normally closed valve in saidconnection, pressure responsive means for moving said valve, and aconnection from said first conduit to said pressure responsive meanswhereby said valve is movable in response to an increase in pressure insaid first conduit resulting from non-operation of at least one of thegenerators for opening said valve whereby a portion of the fuel in thegenerator supply conduit is by-passed to the burner.

6. Fuel flow controlling means for a power plant including a number ofinternal combustion gas generators, and a burner through which gas fromthe generators passes and in which additional fuel is burned, said fuelflow controlling means including a conduit supplying fuel to thegenerators, and another conduit supplying fuel to the burner, and meansresponsive to an increase in pressure in said first conduit resultingfrom non-operation of at least one of the generators for delivering apart of the fuel from said first conduit to said second conduit.

RICHARD J. COAR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 644,741 Guthrie Mar. 6, 19001,479,802 Glendenning Jan. 8, 1924 2,139,284 Rieseler Dec. 6, 19382,160,218 Kingston et a1 May 30, 1939 2,179,628 Heinzelmann Nov. 14,1939 2,238,905 Lysholm Apr. 22, 1941 2,266,533 Brisbane Dec. 16, 19412,292,288 Pateras Pescara Aug. 4, 1942 2,343,375 Herman Mar. 7, 19442,374,844 Stokes iay l, 1945 2,379,455 Prince July 3, 1945 2,419,171Simpson et a1. Apr. 15, 1947 2,422,808 Stokes June 24, 1947 2,447,124Kalitinzky et al Aug. 17, 1948 FOREIGN PATENTS Number Country Date523,468 Great Britain July 15, 1940

